1. Field of the Invention
2. Description of the Prior Art
The present invention relates to a two-stage fluid control valve that has an actuating element, a preliminary stage, and a main stage.
Various designs of fluid control valves are known from the prior art. Valves of this kind are used for example in supplying hydraulic pressure to wheel brakes in vehicle brake systems. An embodiment in the form of a two-stage valve with a preliminary stage and a main stage is designed to permit the opening of the valve even in the presence of powerful differential pressures. The differential pressure at the valve exerts a closing action on the valve. The opening of the preliminary stage slightly reduces the differential pressure so that the main stage can then be opened with a reduced expenditure of energy. In valves of this kind, usually spring elements are used, which have to be overcome in order to open the preliminary and/or main stage and which then automatically close the valve again after the decrease of the switching pressure. Valves of this kind, however, have a relatively large number of parts so that on the one hand, the manufacture and on the other hand, the assembly is relatively cost-intensive.